1. Field of the Invention
The invention relates to a hybrid vehicle that is equipped with an engine and an electric motor.
2. Description of the Related Art
There is known a hybrid vehicle that is equipped with an engine and a motor (an electric motor) for driving driving wheels, a generator (an electric power generator) capable of generating an electric power by a power of the engine, and a power split mechanism that splits the power of the engine and transmits the split power to the driving wheels and the generator.
The power split mechanism of this hybrid vehicle includes a sun gear that is coupled to the generator, a ring gear that is coupled to the motor and the driving wheels, a pinion gear that meshes with the sun gear and the ring gear, and a carrier that supports the pinion gear and is coupled to the engine.
In this hybrid vehicle, the power of the engine is transmitted to the generator via the carrier and the sun gear, and an electric power is thereby generated by the generator. Besides, the power of the engine is transmitted to the driving wheels via the carrier and the ring gear, and the driving wheels are thereby driven. Furthermore, the output of the engine can be supplemented (assisted) by outputting the power of the motor to the ring gear.
Besides, this hybrid vehicle is provided with a power switch for allowing a driver to boot and stop a hybrid system (a vehicle system).
It should be noted herein that the aforementioned hybrid vehicle includes a hybrid vehicle that is configured to make a transition to a limp mode in which the vehicle runs only by the power of the motor, by stopping the operation of the generator and the operation of the engine if an abnormality occurs in the generator.
However, in this hybrid vehicle, if the operation of the engine is stopped while running at high speed, the carrier is stopped from rotating, so that the difference between the rotational speed of the ring gear and the rotational speed of the carrier increases. In some cases, therefore, over-rotation of the pinion gear occurs.
Thus, in Japanese Patent Application Publication No. 2010-264852 (JP-2010-264852 A), there is proposed a hybrid vehicle in which the operation of an engine is controlled so as to prevent over-rotation of a pinion gear in making a transition to a limp mode.
In the conventional hybrid vehicle disclosed in Japanese Patent Application Publication No. 2010-264852 (JP-2010-264852 A), over-rotation of the pinion gear is prevented by continuing the operation of the engine. However, if the operation of the engine is stopped through the performance of an operation of stopping the hybrid system during running, over-rotation of the pinion gear may occur.